• Y Shimizu, T Suga, T Maeno, H Tsukagoshi, T Kawata, T Narita, T Takahashi, S Ishikawa, Y Morishita, T Nakajima, F Hara, T Miura, and M Kurabayashi.
• Department of Medicine and Biological Science, Gunma University Graduate School of Medicine, Maebashi, Gunma, Japan. yshimizu@med.gunma-u.ac.jp
• Clin. Exp. Allergy. 2004 Nov 1; 34 (11): 1719-24.

BackgroundMast cells (MCs) arise from haematopoietic stem cells. We have recently reported that CD34(+) progenitors derived from human bone marrow (BM) develop into tryptase+, chymase+ MCs when cultured in the presence of recombinant human stem cell factor (rhSCF) and recombinant human IL-6 (rhIL-6). In an experiment for the expression of chymase during differentiation, chymase+ cells were detected in human BM, but tryptase+ cells were not found.ObjectiveThe purpose of this study was to show the appearance of chymase+ cells in CD34(+) cells with an origin different from MC differentiation.MethodsCD34(+) cells from human BM were sorted with anti-CD117 monoclonal antibody (mAb), and cytospins of CD34(+), CD34(+)CD117(+), or CD34(+)CD117(-) were prepared. These cells were cultured with rhSCF+rhIL-6 for 12 weeks. Some of the cells were subjected to either histological stain with Wright-Giemsa or immunocytochemistry with anti-chymase mAb. Real-time RT-PCR was also performed to compare the transcriptional level of chymase from each cell preparation.ResultsChymase was expressed in CD34(+) cells as well as human MCs by immunocytochemistry. Substantial CD34(+)CD117(-) cells, but not CD34(+)CD117(+) cells, were stained immunocytochemically with anti-chymase mAb. For 1 week culture with rhSCF+rhIL-6, no cells expressed chymase in any preparation. Real-time RT-PCR revealed positivity for chymase mRNA in CD34(+) cells, but it reduced at 1 week of culture, and increased as cells developed into MCs. Chymase mRNA in CD34(+)CD117(+) cells was negligible compared with that in CD34(+)CD117(-). Tryptase mRNA was below the detectable level in CD34(+) cells, and increased along with MC differentiation. After 12 weeks of culture, CD34(+)CD117(+) developed predominantly into MCs, whereas CD34(+)CD117(-) developed into monocytes/macrophages.ConclusionOur findings suggested that chymase is present not only in MCs but also in CD34(+)CD117(-) BM progenitors, but that its origin is different from the MC lineage.

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